Diagnosis and management of hymenoptera venom allergy: British Society for Allergy and Clinical Immunology (BSACI) guidelines

April 29, 2011 11:21 am

Summary

This guidance for the management of patients with hymenoptera venom allergy has been prepared by the Standards of Care Committee (SOCC) of the British Society for Allergy and Clinical Immunology (BSACI). The guideline is based on evidence as well as on expert opinion and is for use by both adult physicians and pediatricians practising allergy. During the development of these guidelines, all BSACI members were included in the consultation process using a web-based system. Their comments and suggestions were carefully considered by the SOCC. Where evidence was lacking, consensus was reached by the experts on the committee. Included in this guideline are epidemiology, risk factors, clinical features, diagnostic tests, natural history of hymenoptera venom allergy and guidance on undertaking venom immunotherapy (VIT). There are also separate sections on children, elevated baseline tryptase and mastocytosis and mechanisms underlying VIT. Finally, we have made recommendations for potential areas of future research.

Executive Summary

  1. Patients experiencing a systemic reaction (SR) to wasp or bee stings should be referred to an allergy specialist for investigation and management.
  2. In the United Kingdom, wasp venom allergy is more common. Bee venom allergy usually occurs in beekeepers, their household members or where there is occupational risk.
  3. Venom allergy is a common cause of anaphylaxis and may be fatal. The main features of SRs are rapid onset generalized urticaria, angio-oedema, bronchospasm/laryngeal oedema and hypotension with collapse and loss of consciousness. Hypotension is the dominant feature and may occur alone.
  4. Demonstration of venom-specific IgE is the cornerstone of diagnosis and skin testing (skin prick and intradermal) remains the first line of investigation. All patients should be tested to both venoms. While double-positive intradermal skin tests to both bee and wasp venoms are rare, dual-positive serum specific IgE is common even in the presence of clinical allergy to a single member of the hymenoptera family.
  5. Baseline tryptase should be measured in all patients with SRs, as those with raised levels have a higher risk of severe SRs.
  6. Patients with a history of SR should be immediately provided with a written emergency management plan, an adrenaline auto-injector and educated in its use.
  7. Venom immunotherapy (VIT) is effective in 95% of patients allergic to wasp venom and about 80% of those allergic to bee venom.
  8. VIT is recommended for all patients with a severe SR after a sting and in many patients after a SR of moderate severity.
  9. VIT is usually not indicated for less severe sting induced SRs unless additional risk factors are present for example: a raised baseline tryptase, a high likelihood of future stings, (bee keeping, or occupational exposure), or effect on quality of life (QOL).
  10. Children generally have less severe reactions than adults and a better prognosis and therefore VIT should only be considered for the small percentage that have severe sting-induced systemic allergic reactions.
  11. VIT must not be undertaken in the absence of demonstrable venom-specific IgE. In patients with a recent history of anaphylaxis or SR, where venom specific IgE is not demonstrable, allergy testing should be repeated.
  12. VIT should be carried out only by allergy specialists with experience and knowledge in this field and in centres undertaking VIT in significant numbers of patients and where the team has expertise in treating anaphylaxis.
  13. In the United Kingdom, the usual duration of VIT is 3 years. Longer or even life-long treatment in patients with a raised baseline tryptase is not advocated in the United Kingdom because this is not evidence-based.
  14. Many patients with a raised baseline tryptase and a SR have an indolent form of ‘mastocytosis’ and are at higher risk of SRs during VIT although VIT remains the treatment of choice.
  15. An adrenaline autoinjector should be provided during up-dosing of VIT and British Society for Allergy and Clinical Immunology (BSACI) also recommends its long-term prescription for the following:
    a. If during VIT the patient continued to experience allergic reactions
    b. After VIT, those at continuing risk of multiple stings, e.g. those with an occupational risk or a beekeeper
    c. After VIT, patients with an elevated baseline tryptase or mastocytosis.
  16. Patients should be advised on ways of minimising their risk of further stings.

Introduction

This guidance is intended for use by specialists involved in the investigation and management of patients with hymenoptera venom allergy. This updates the previous BSACI position paper [1]. It is recommended that all patients experiencing a SR in response to insect stings be referred to an allergy specialist for further investigation.

Evidence for these recommendations was collected by electronic literature search using the key words – hymenoptera, venom, allergy, VIT in combination with skin test, anaphylaxis, mastocytosis, bee keeper, rush, ultra rush, protocols, antihistamine, epidemiology, cross reactivity, b-blockers, angiotensin-converting enzyme (ACE) inhibitors, basophil activation test (BAT) and CD63. Each article was assessed for its suitability.

Epidemiology

Questionnaire-based studies have shown that 56–94% [2] of the population are stung by an insect of the hymenoptera family at least once in their lifetime. While the prevalence of sensitization varies between 9.3% and 38.7% [3] in the adult population, large local reactions (LLR) occur in 2.4–26.4% [3–6] and SRs in 0.3–7.5% [5–10]. The differences between studies have been attributed at least in part to confounding variables including geographical location, data collection technique, definition of anaphylaxis and degree of exposure. In bee keepers and their family members, the sensitization rate to bee venom is 30–60% [11], the prevalence of local reactions is 9–31%, and the prevalence of SRs is 14–32%. Venom allergy is an important cause of anaphylaxis accounting for about one quarter of cases where the cause was determined in adults [12]. Fatalities following insect stings are rare and occur in 0.03–0.48 per 100 000 inhabitants per year [2, 3, 11]. These data are largely from studies carried out in the United States and Europe. There are no published data on prevalence of hymenoptera venom allergy from the United Kingdom. However, Pumphrey [12, 13] reported that between 1992 and 2001 in the United Kingdom, 47 out of 214 deaths, due to anaphylaxis, were caused by bee or wasp stings and the average age of death was 50 years [13].

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